Imre Lakatos also presented evidence that the Michelson-Morley experiment was irrelevant to Einstein (and virtually everyone else) -- gaining its fame only many years later and in hindsight. Lakatos went so far as to maintain that there were no such things as 'crucial experiments' in science (see his article "Anomalies versus 'crucial experiments'", reprinted in vol. 2 of his collected works.) This of course also dates from the same time frame that Ted mentioned for his own expertise, as Lakatos died in 1973 (or maybe it was 1974).

When Michelson was awarded the Nobel Prize in 1907, there was no mention of the M-M experiment.

I believe Einstein did know of the negative result of the Michelson-Morley
experiment before he wrote his seminal work on special relativity. Is there
any doubt about this?

***

Ted replies:
Yes, Moorad, there is considerable doubt about this. Let me say right away
that my knowledge of this is not really up to date, in terms of the
historical scholarship on the development of Einstein's theory, but when my
knowledge was up to date a quarter century ago, a good argument could be
made that he had not actually heard of the MM Expt at the time he wrote his
early papers on special relativity (pub 1905). There were several other
expts by others, trying to detect the earth's motion through the ether in
other ways, and he did know about some of those, but maybe not MM.

For a clear presentation of this argument, see Gerald Holton's essay,
"Einstein, Michelson, and the 'Crucial' Experiment," Isis 60 (1969): 133-97,
or as reprinted in Holton's book, "Thematic Origins of Scientific Thought."
Holton concludes, after surveying all of the evidence available to him, that
the primary sources (that is, what was actually said at the time) "tell a
story for which the secondary sources had not prepared us. It is a scenario
of which we cannot, in the nature of the case, be absolutely certain, but
one which is highly probable. Indeed, the role of the Michelson experiment
in the genesis of Einstein's theory appears to have been so small and
indirect that one may speculate that it would have made no difference to
Einstein's work if the experiment had never been made at all."

My own view is (and I caution people that I am no expert on Einstein) that
the crucial insights for Einstein were theoretical and conceptual, not
experimental. Consider for a moment the difference in how one explains what
happens in these two cases:

(1) hold a solenoid stationary (relative to you), and move a bar magnet
through it. A current is induced, but why? The magnetic field is
moving/changing, but the electric charges in the solenoid are not. The emf
comes from the changing magnetic field, not from the moving charges.

(2) hold a bar magnet stationary, and move the solenoid through it. A
current is induced, but why? The magnetic field is not changing, but the
charges are moving. The emf comes from the moving charges, not from a
changing magnetic field.

Einstein was committed to the view that the relative motion of the magnet
and the coil was the only factor that should matter, and he sought an
explanation that was symmetric to the two cases. You know a lot more
physics than I do, Moorad, so you can see more clearly than me where this is
going...

Ted

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